1. Field of the Invention
The present invention relates to power transmission members such as pulleys.
2. Description of Related Arts
In recent years, as a variable speed pulley so adapted that its effective diameter for a belt can be changed, a variable speed pulley of such a type that a flat belt is wound around a power transmission ring which can be eccentric from an axis of the pulley with it being fitted in a V-groove of the pulley has been provided. In this type of variable speed pulley, torque is transmitted between a member forming the V-groove and the power transmission ring. However, the area of a contact portion therebetween is narrow, so that surface pressure is significantly increased. In the above-mentioned contact portion, there exists a complicated contact state where rolling movement for torque transmission and sliding movement for eccentricity are mixed.
On the other hand, a metal was conventionally used as a material composing the power transmission ring, so that there were some problems. For example, the power transmission ring was seized, or the member forming the V-groove greatly wore.
For this problem, it is considered that resin be used for the power transmission ring. When a general resin is used for the power transmission ring, the power transmission ring greatly wears, and friction is unstable. As a result, consideration has been given to cases where the torque to be transmitted is not stabilized and the contact portion is melted.
In other words, as a resin molded member used for the power transmission ring, the member itself must have good compatibility with a counterpart member, although it is superior in wear resistance. Moreover, it must have a proper coefficient of friction which is stable irrespective of temperature.
In recent years, a pulley which was conventionally mainly composed of a metal has been replaced with one made of resin as automobile parts have been made small in size and light in weight and have been lowered in cost. A general pulley had the same problems as the above-mentioned power transmission ring.
In order to solve such problems, a power transmission member constructed by molding a resin material obtained by mixing an aromatic polyamide fiber, a non-linear inorganic filler and graphite with phenol resin has been considered (see JP-A-8-23-573, which is assigned to the assignee of the present application for example). The applicant of the present invention has encountered a case where the above material has insufficient in strength when it is applied to the power transmission ring. In such a case, it is considered that a reinforcing metal member is embedded in the resin material. If the reinforcing metal member is embedded, however, it costs much to manufacture the reinforcing metal member. Further, the cost for resin molding rises because the reinforming metal member is embedded.